Amplification systems for electronic musical instruments, particularly electric guitars are well known in the art. Generally, such amplifiers can be large, bulky devices driven by an AC power source and requiring separate, loose interconnection cables to both the guitar(s) and speaker(s). Due to the size and power requirements of such systems, they can have a limited utility. U.S. Pat. No. 4,532,847 to Youngblood appears to disclose such a system.
To enable musicians to practice playing their electric instruments when an AC power source is not available, portable battery-operated systems have been developed. Typically, as shown in FIG. 1, such amplifiers 12 are connected to an electric guitar 2 by a loose interconnection cable 8 with plug 6 being inserted in output jack 4 of guitar 2 and plug 10 being connected to amplifier 12. To monitor output from the amplifier without disturbing people nearby, a set of lightweight headphones 18 is connected to amplifier 12 via headphone cable 16 at the end of which is plug 14. Due to the presence of the interconnection cable and the physical size and weight of the amplifier unit 12 (e.g., 6.2 inches by 4.2 inches by 1.4 inches and approximately 15 ounces), these amplifier systems can be very clumsy and awkward to use, especially by a musician who changes positions (i.e., stands up or moves around) or alters the control settings. Consequently, musicians utilizing such systems typically remain seated with the amplifier resting nearby. An amplifier system similar to that shown in FIG. 1 is disclosed by U.S. Pat. No. 4,085,365 to Reick.
The awkwardness of utilizing a heavy, bulky amplifier with loose-hanging interconnection cables is discussed in U.S. Pat. No. 4,245,136 to Krauel, Jr. To obviate these problems, the device shown in this reference mounts the amplifier circuitry and batteries within the headphone. As a result, the overall size and weight of the headphones is significantly increased, making the amplifier uncomfortable to use, especially during long playing sessions. In addition, positioning the amplifier circuitry in the headphones can make the controls difficult to find and adjust, because the user, when wearing the headphones, cannot see where they are located. The number of controls employed should, therefore, be limited.
U.S. Pat. No. 4,428,268 to Ingoglia discloses another type of guitar amplifier which operates without using electrical energy. Specifically, the amplifier system includes a transmittal pickup plate on the guitar which is attached to sound transmittal tubes 18 that extend to earpieces 28. The sound quality of such an amplifier system tends to be of lower quality than that of an electrical amplifier system.